A chucking device has heretofore been developed as a device for removably holding an optical disk such as a compact disk or the like (hereinafter simply referred to as a “disk”). In general, the chucking device is attached to a top portion of a motor and is rotated together with the motor to thereby rotate the disk.
In keeping with a recent demand for a low-profile disk drive apparatus, it becomes essential to reduce the thickness of a motor provided with a chucking device. In this type of motor, the thickness of the chucking device accounts for a large percentage of the overall thickness of the motor. Therefore, reduction in thickness of the chucking device is very effective in providing a low-profile disk drive apparatus.
A conventional chucking device that realizes thickness reduction is disclosed in Japanese Patent Laid-open Publication No. 2005-251298 (JP2005-251298A). The chucking device includes claw members for holding a disk. Each of the claw members has a disk holding surface that makes contact with the disk and a pair of downwardly extending guide surfaces formed on the opposite circumferential sides of the disk holding surface for guiding radial inward movement of each of the claw members.
Along with the increase in a quantity of information stored in a disk, it is a recent trend that a laminated disk, such as a DVD or the like, formed by bonding two disks together is frequently used in recent years. Since the laminated disk has an increased thickness, a low-profile chucking device is incapable of exerting a disk holding force (hereinafter referred to as a “holding force”) great enough to hold the laminated disk. Particularly, in case of the claw members disclosed in JP2005-251298A, it is difficult to increase a circumferential width of the disk holding surface because the downwardly extending guide surfaces are formed on the opposite sides of the disk holding surface. This means that the chucking device disclosed in JP2005-251298A is unable to exert a holding force great enough to hold a disk having an increased thickness.
It would be thinkable that the spring force of a coil spring is increased to obtain the holding force as required. If the spring force is increased, however, it becomes hard for the claw members to move in a radial inward direction when the disk is mounted to the chucking device. This poses a problem in that the disk mounting force is increased.
In keeping with the thickness reduction of a disk drive apparatus, the moving distance of a disk required in traversing a motor becomes small. This reduces the force by which the disk is mounted to a chucking device. Therefore, it is necessary for the chucking device to have a structure that allows the disk to be mounted with ease.